It has been a history of more than 4,000 years for people to get the cognition of hemorrhoid. Up to now, the conventional methods for treating internal hemorrhoid include injection sclerotherapy, rubber band ligation and various kinds of surgical excisions. All these methods are treatments against the hemorrhoid per se and intended to make the hemorrhoid dwindled or disappeared. Among surgical excisions of hemorrhoid, a method named PPH surgery is to perform a procedure for prolapse and hemorrhoids with the assistance of a circular stapler.
U.S. Pat. No. 6,083,241 discloses a circular stapler, as shown in FIG. 1, its staple head assembly 40 includes an anvil 60 and a staple barrel 41 provided with a staple cartridge, a staple pusher and staples inside, and the anvil 60 and the staple barrel 41 are disposed oppositely. During surgery, the hemorrhoidal mucosa is pulled into the staple barrel 41, and is cut annularly while the anastomosis is performed between the anvil 60 and staple barrel 41. The opening on the housing of staple barrel 41 is significantly small, which can only be served to form a passageway 42 for string guiding instrument 140 to pass through the staple barrel 41 and to pull the purse-string sutured tissue into the staple barrel 41.
Currently, the staple barrel of commonly-used circular stapler, as the limitations in its structure, may provide limited viewing window and operating space for surgeon during the using process in surgery, which is bad for pulling-in operation on tissues. Besides, the accommodating space of staple barrel is also too limited to accommodate more to-be-excised tissues, which has great limitations, while a plurality of hemorrhoids need to be cut at one time in surgery (such as TST surgery against a plurality of hemorrhoids).
In addition, according to the clinical experience of surgeons, if an overlong tissue is pulled into the staple barrel, the postoperative performance may be not well. For example, it can be learned from medical knowledge that: a dentate annular line which can be seen at the commissure of anal canal skin and rectal mucosa and is enclosed by the edge of anal valves and the lower end of anal columns, is named dentate line. As the tissue structure above and below the dentate line are different, more than 85% of rectum and anus diseases occur near the dentate line. The dentate line is an induction area of defecation reflex, so when the excrement arrives at the anal canal via the rectum, the nerve terminal receptor at dentate line area will be stimulated and then make the anal canal open reflectively to discharge the excrement. If the tissues pulled in are too long to lead to excise dentate line in surgery, it will cause decreased defecation reflex on postoperative patient, which may make some adverse reactions such as constipation or sensory fecal incontinence occurred.
However, the conventional circular stapler only has scale indication for indicating the depth of stapler into anus on the outer surface of staple barrel (such as reference numeric 49 in FIG. 1), which can't provide criterion for surgeon to estimate the amount of hemorrhoid mucosa tissues pulled into staple barrel. As a result, the amount and depth of mucosa tissues pulled into staple barrel cannot be determined, which may cause too many tissues pulled into staple barrel to make poor postoperative performance on patients.